In recent years, various batteries have been used as power supplies for mobile terminals, electric vehicles, hybrid cars, and so on, and various battery containers for such batteries have been proposed. For example, a method of manufacturing a battery container including a case member for containing a battery member therein and a closing (member for closing an opening, in which a projection of the case member is joined with a projection of the closing member by welding, is known (see, for example, Patent Literature 1).